A Literature Review of Nitrogen Availability Indices for Use in Urban Landscapes

Abstract

Managers of urban landscapes are required to maintain aesthetic qualities of plants and so must ensure that vegetation has adequate nitrogen to grow and thrive. Soil organic matter decomposition and nitrogen mineralization facilitated by soil microorganisms are the primary determinants of soil nitrogen availability. Therefore, investigations of soil nitrogen pools, organic matter, and soil microbial populations should help urban landscape managers refine diagnostic tools and prescription fertilization for urban vegetation. Foliar assessments can be used to measure nitrogen the plant has acquired, but such assessments do not reveal information about current or future plant nitrogen acquisition. Soil nitrogen analyses can be used to measure the current nitrogen available for plant uptake as well as the amount that will potentially be available at some time in the future. Total soil organic matter changes occur primarily particulate organic matter (POM) fractions, and positive correlations have been identified between POM nitrogen, soil microbial nitrogen, and potentially mineralizable nitrogen. Consequently, examinations of POM fractions potentially indicate changes in soil organic matter and nitrogen availability. To improve existing standards for determining nitrogen status and needs of urban landscape plants, soil and plant nitrogen evaluation must be improved and correlated with plant nitrogen demand and soil nitrogen supply.